Proppant transport in secondary Sand fracturing using Eulerian-Eulerian multiphase model Approach

Abstract

Secondary sand fracturing, an innovative hydraulic fracturing technique, divides the injection of proppant into two stages, altering the reservoir's rock mechanics and fracturing fluid flow paths, thus effectively controlling fracture creation and improving the effectiveness of proppant placement. This methodology facilitates fracture height control and enhances fracture conductivity, benefiting production rate. Despite abundant literature on proppant transport, limited attention has been paid to exploring the specific aspects of secondary sand fracturing. In this study, the Eulerian-Eulerian multiphase model was used to simulate the proppant transport in secondary sand fracturing for the first time. This model accounts for turbulence and the interplay between proppant particles, thus enabling a comprehensive integration of fluid and particulate phases. The effects of proppant performance, fracturing fluid performance, and fluid flow rate on proppant placement were analyzed. In the first sand-addition stage, an innovative sanding index was proposed to evaluate the effectiveness of proppant placement. Combined with the orthogonal experiment, the fluid flow rate significantly influences proppant placement. An escalated flow rate augments both the sandbank leading edge and laying lengths, concurrently diminishing the equilibrium height and the sanding index. In the second sand-addition stage, the equilibrium height increases with the increase of sand ratio, decreases with the increase of flow rate and fluid viscosity, and first increases and then decreases with the increase of particle size and proppant density. This study enriches the comprehension of proppant placement and its governing elements within hydraulic fracturing, thereby furnishing a more empirical and theoretically sound foundation for optimizing secondary sand fracturing practices.